The present invention relates to a composite prepreg for molding composed of a fabric material of aromatic polyamide fibers having been subjected to surface modification and impregnated with an organic resinous binder or, more particularly, to an aromatic polyamide fiber-based composite prepeg capable of giving molded articles having excellent mechanical strengths by virtue of the greatly improved adhesive bonding between the surface of the aromatic polyamide fibers and the organic resinous binder impregnating the fabric material of the aromatic polyamide fibers.
Fabric materials, e.g. cloths, of aromatic polyamide fibers have various excellent and advantageous properties including low density, high strength, high elasticity, heat resistance, flame retardancy and others so that they are highlighted as a heat-resistant base material of various kinds of molding prepregs or molding compounds as impregnated with an organic resinous binder. A problem in such a prepreg is the relatively low adhesive bonding strength between the surface of the aromatic polyamide fibers and the organic resious binder impregnating the fabric material of the fibers so that the articles shaped by molding such a prepreg cannot have a sufficiently high mechanical strength as expected. Accordingly, it is eagerly desired to develop a means for the improvement in this regard.
Various proposals and attempts have been hitherto made to increase the adhesive bonding strength between the surface of aromatic polyamide fibers and an organic resinous binder for the impregnation of the fibers including the chemical treatment, e.g. chemical etching and primer treatment, corona discharge treatment and the like. These methods, however, cannot be sufficiently efficient due to the high chemical stability of the aromatic polyamide fibers.